package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.service.impl.ShopServiceImpl.CACHE_REBUILD_EXECUTOR;
import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time , TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    /*
    * 逻辑过期
    * */
    public void setWithLogicalExpire(String key, Object value, Long time , TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    /*
     * 缓存穿透
     * */
    public <R,ID> R queryWithPassThrough(
            String keyPrefix , ID id, Class<R> clazz, Function<ID,R> dbFallback,Long time , TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回
            //  缓存命中，直接返回店铺数据
            return JSONUtil.toBean(json, clazz);
        }
        //判断命中是否是空值
        if (json != null) {
            //返回一个错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在写入redis, 并设置时间
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }


    public <R,ID> R queryWithLogicalExpire
            (String keyPrefix , ID id,Class<R> clazz, Function<ID,R> dbFallback, Long time , TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.存在，直接返回
            //  缓存命中，直接返回店铺数据
            return null;
        }
        //4.命中，需要判断过期时间，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, clazz);
        LocalDateTime expireTime = redisData.getExpireTime();//过期时间
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，返回店铺信息
            return r;
        }
        //5.2已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取成功
        if (isLock) {
            // TODO 6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    //1.查询数据库
                    R r1 = dbFallback.apply(id);
                    //2.写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4失败，返回过期的商品信息
        return r;
    }


    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
